1. Field of the Invention
The present invention relates to a boring device for a lining material having been applied onto the inner surface of a pipe line having a branched portion, which device can bore the lining material in the branched portion to communicate the branched pipe line to the main pipe line, and more particularly, to a boring device which is inserted from the branched pipe line having a smaller diameter and to the branched portion where the lining material is bored.
2. Description of the Prior Art
In general, a lining treatment for pipe lines, chiefly those buried in the ground, such as gas conduits and city water pipe lines, is carried out for the purpose of repairing or reinforcing the pipe lines.
As a method for lining, there is known a method which is carried out in such a manner that a tubular lining material made of a flexible material, which has been provided on the inner, leading surface thereof with a binder, is annularly fixed at one end thereof and fluid pressure is applied to the back surface of the annularly fixed portion to form a turning point such that the lining material is turned inside out which allows the turning point to advance within the pipe line thereby inserting the evaginated lining material into the pipe line, while pressing the surface of the lining material, onto which the binder has been applied, against the inner surface of the pipe line by the fluid pressure and solidifying the binder to effect bonding. This method has a number of merits. It is unnecessary to dig up a pipe line over its full length and the method is operable simply by digging the pipe line only at both terminal ends thereof to be treated, and the lining work itself can be done within a very short period of time even for a long pipe line. In recent years, therefore, this method has attracted special public attention.
In case a pipe line is lined according to this method wherein a tubular lining material is bonded to the entire inner surface of the pipe line, however, a passage with branch pipe lines off the main pipe line will have their entrances blocked. In the case of a gas conduit, for example, such problem will not arise in a high or middle pressure pipe line as a trunk conduit, because the line is usually devoid of any branched portion. In the case of a terminal low pressure pipe line, however, there are a number of branched supply pipe lines for supplying gas according to the unit of users, for example, the number of families.
Thus, the passages to the supply pipe lines will be blocked when the low pressure pipe line is lined according to the above mentioned method. In such a case, digging up the branched portions from the ground for boring the lining material after the lining treatment will make no substantial difference from digging up the entire pipe line over its full length, thus losing the greatest merit of this lining method.
Accordingly, there is a demand for developing a simple and easy means for boring the applied lining material at the branched portions after the pipe-lining treatment to communicate the branched pipe lines to the main pipe line without digging up the branched portion from the ground.
A method is known wherein a cart movable by remote control and a device for detecting a branched portion to a branched pipe line, such as a TV-camera, movable together with the cart, are disposed within a lined pipe line, and a boring head installed on the cart is moved freely in both circumferential and radial directions within the pipe line to the branched portion by remote operation to bore the lining material blocking a path to the branched pipe line (British Pat. No. 2,092,493).
In this device for boring, however, a means for exactly detecting the position of an opening to a branched pipe line on the inner surface of the lined pipe line is quite necessary and a driving means for moving the boring head is also necessary so that the device becomes inevitably complicated as a whole. Thus, such a device and method cannot be applied to a pipe line having bends or to a pipe line of a small diameter.
A method disclosed in Japanese Laid-open Patent Appln. No. Sho. 55-41274 is known, for example, as a method for boring a lining material at branched portions of a pipe line after applying the lining material onto the pipe line, without digging it up from the ground. This method comprises introducing an insert mass having a flexible conduit passing through the central core of the mass and extending backward into a branched portion of a pipe line the inner surface of which has been bonded to the lining material, allowing pressure to act on the back of the insert mass while evacuating the air occupying the space in front of the insert mass through the flexible conduit thereby leading the flexible conduit to the opening for the branched pipe line, and thereafter sending a hot blast through the flexible conduit to the lining material bonded to the pipe line to bore it by fusion.
Another method is disclosed in Japanese Laid-open Patent Appln. No. Sho. 58-49211 wherein an opening to a branch portion existing in a pipe line is once clogged with a stopper prior to the application of a lining material and the stopper is then allowed, after the application of the lining material, to become exothermic to use itself as a heating tool thereby boring the lining material bonded to the stopper by fusion.
According to the above known prior art wherein the insert mass or the stopper is allowed to advance and become located at the branched portion of the pipe line by fluid pressure, however, it is extremely difficult in the case of a small and multiple complicated bent branched pipe line to lead the insert mass or the stopper to the branched portion by fluid pressure.
As the method disclosed in the above-mentioned Japanese Laid-open Patent Appln. No. Sho. 55-41274 wherein the boring operation has to be performed by a hot blast, the boring operation is not easy. In addition, since a portion of the binder will flow into the branched pipe line and is solidified therein on bonding the lining material to the inner surface of the main pipe line, it is extremely difficult to fuse the lining material including such solidified binder for effecting the boring.
In the method disclosed in the above-mentioned Japanese Laid-open Patent Appln. No. Sho. 55-49211 wherein the stopper has to be initially mounted to the branched portion prior to the application of the lining material, it is not easy to mount the stopper correctly to the opening of the branched portion. Further, this method has such a drawback that it cannot be applied to a pipe line to which a lining material has already been applied.
Under such circumstances, the present inventors have already invented a boring device which comprises a first flexible coil spring, a second more flexible compression coil spring connected to the front end of the first coil spring and an electric heater mounted to the tip of the second coil spring, operated in such a manner that the springs are introduced into a pipe line while rotating the first coil spring so as to allow the electric heater to locate in the branched portion, and electricity is sent to the heater to burn out the lining material. This approach is applicable to a pipe line for which the lining treatment has been finished, and is capable of being led to the branched portion through a branched pipe line having a small diameter and being curved and bent, and easily capable of boring the lining material even in the case of the branched pipe line having been filled with a large amount of a binder flowed thereinto (Japanese Laid-open Utility Model Appln. No. Sho. 61-39400).
In this device wherein the boring device is introduced while rotating the first coil spring and rotationally shaking the front electric heater by the resiliency of the second coil spring, however, the electric heater may thrust, at a joint such as LM joint in the pipe line, into a slit between the end of a straight pipe and the joint whereupon the weaker second coil spring buckles and is damaged to make it impossible to move the heater forward beyond that point. Accordingly, the present inventors further developed a boring device wherein the electric heater is surrounded with a thermoplastic resin to shape a block approximately in the form of a circular truncated cone mounted at the tip of the second coil spring (Japanese Utility Model Appln. No. Sho. 60-18915).
The device disclosed in the above mentioned Japanese Utility Model Appln. No. Sho. 60-18915 wherein the electric heater is shaped to have a slanted side surface by coating with a thermoplastic resin can smoothly be moved forward within the branched pipe line in compliance with the curvature of the pipe line, avoiding a step formed at the LM joint or the like and a barrier, such as flash. However, quite often the electric heater led to the branched portion did not function to send electricity thereto.
This situation caused by disconnection of the transmission wires is a phenomenon occurring in the coating of the resin or within the coil spring. It is apparent that this is ascribable to the transmission wires being twisted off.